### jsoncons::basic_json_visitor

```cpp
#include <jsoncons/json_visitor.hpp>

template <
    typename CharT
> class basic_json_visitor
```

Defines an interface for producing and consuming JSON events. 

Aliases for common character types are provided:

Type                |Definition
--------------------|------------------------------
json_visitor    |`basic_json_visitor<char>`
wjson_visitor   |`basic_json_visitor<wchar_t>`

#### Member types

Member type                         |Definition
------------------------------------|------------------------------
`char_type`|CharT
`string_view_type`|A non-owning view of a string, holds a pointer to character data and length. Supports conversion to and from strings. Will be typedef-ed to the C++ 17 [std::string view](http://en.cppreference.com/w/cpp/string/basic_string_view) if C++ 17 is detected or if `JSONCONS_HAS_STD_STRING_VIEW` is defined, otherwise proxied.  

#### Public event producer interface

    void flush(); (1)

    bool begin_object(semantic_tag tag=semantic_tag::none,
                      const ser_context& context=ser_context()); (2)

    bool begin_object(std::size_t length, 
                      semantic_tag tag=semantic_tag::none, 
                      const ser_context& context = ser_context()); (3)

    bool end_object(const ser_context& context = ser_context()); (4)

    bool begin_array(semantic_tag tag=semantic_tag::none,
                     const ser_context& context=ser_context()); (5)

    bool begin_array(std::size_t length, 
                     semantic_tag tag=semantic_tag::none,
                     const ser_context& context=ser_context()); (6)

    bool end_array(const ser_context& context=ser_context()); (7)

    bool key(const string_view_type& name, 
              const ser_context& context=ser_context()); (8)

    bool null_value(semantic_tag tag = semantic_tag::none,
                    const ser_context& context=ser_context()); (9) 

    bool bool_value(bool value, 
                    semantic_tag tag = semantic_tag::none,
                    const ser_context& context=ser_context()); (10) 

    bool string_value(const string_view_type& value, 
                      semantic_tag tag = semantic_tag::none, 
                      const ser_context& context=ser_context()); (11) 

    bool byte_string_value(const byte_string_view& source, 
                           semantic_tag tag=semantic_tag::none, 
                           const ser_context& context=ser_context()); (12) (until 0.152.0)

    template <typename ByteStringLike>
    bool byte_string_value(const ByteStringLike& souce, 
                           semantic_tag tag=semantic_tag::none, 
                           const ser_context& context=ser_context()); (12) (since 0.152.0)

    template <typename ByteStringLike>
    bool byte_string_value(const ByteStringLike& souce, 
                           uint64_t ext_tag, 
                           const ser_context& context=ser_context()); (13) (since 0.152.0)

    bool uint64_value(uint64_t value, 
                      semantic_tag tag = semantic_tag::none, 
                      const ser_context& context=ser_context()); (14)

    bool int64_value(int64_t value, 
                     semantic_tag tag = semantic_tag::none, 
                     const ser_context& context=ser_context()); (15)

    bool half_value(uint16_t value, 
                    semantic_tag tag = semantic_tag::none, 
                    const ser_context& context=ser_context()); (16)

    bool double_value(double value, 
                      semantic_tag tag = semantic_tag::none, 
                      const ser_context& context=ser_context()); (17)

    bool begin_object(semantic_tag tag,
                      const ser_context& context,
                      std::error_code& ec); (18)

    bool begin_object(std::size_t length, 
                      semantic_tag tag, 
                      const ser_context& context,
                      std::error_code& ec); (19)

    bool end_object(const ser_context& context, 
                    std::error_code& ec); (20)

    bool begin_array(semantic_tag tag, 
                     const ser_context& context, 
                     std::error_code& ec); (21)

    bool begin_array(std::size_t length, 
                     semantic_tag tag, 
                     const ser_context& context, 
                     std::error_code& ec); (22)

    bool end_array(const ser_context& context, 
                   std::error_code& ec); (23)

    bool key(const string_view_type& name, 
              const ser_context& context, 
              std::error_code& ec); (24)

    bool null_value(semantic_tag tag,
                    const ser_context& context,
                    std::error_code& ec); (25) 

    bool bool_value(bool value, 
                    semantic_tag tag,
                    const ser_context& context,
                    std::error_code& ec); (26) 

    bool string_value(const string_view_type& value, 
                      semantic_tag tag, 
                      const ser_context& context,
                      std::error_code& ec); (27) 

    bool byte_string_value(const byte_string_view& source, 
                           semantic_tag tag, 
                           const ser_context& context,
                           std::error_code& ec); (28) (until 0.152.0)

    template <typename ByteStringLike>   
    bool byte_string_value(const ByteStringLike& source, 
                           semantic_tag tag, 
                           const ser_context& context,
                           std::error_code& ec); (28) (since 0.152.0)

    template <typename ByteStringLike>   
    bool byte_string_value(const ByteStringLike& source, 
                           uint64_t ext_tag, 
                           const ser_context& context,
                           std::error_code& ec); (29) (since 0.152.0)

    bool uint64_value(uint64_t value, 
                      semantic_tag tag, 
                      const ser_context& context,
                      std::error_code& ec); (30)

    bool int64_value(int64_t value, 
                     semantic_tag tag, 
                     const ser_context& context,
                     std::error_code& ec); (31)

    bool half_value(uint16_t value, 
                    semantic_tag tag, 
                    const ser_context& context,
                    std::error_code& ec); (32)

    bool double_value(double value, 
                      semantic_tag tag, 
                      const ser_context& context,
                      std::error_code& ec); (33)

    template <typename T>
    bool typed_array(const span<T>& data, 
                     semantic_tag tag=semantic_tag::none,
                     const ser_context& context=ser_context()); (34)

    bool typed_array(half_arg_t, const span<const uint16_t>& s,
        semantic_tag tag = semantic_tag::none,
        const ser_context& context = ser_context()); (35)

    bool begin_multi_dim(const span<const size_t>& shape,
                         semantic_tag tag,
                         const ser_context& context); (36) 

    bool end_multi_dim(const ser_context& context=ser_context()); (37) 

    template <typename T>
    bool typed_array(const span<T>& data, 
                     semantic_tag tag,
                     const ser_context& context,
                     std::error_code& ec); (38)

    bool typed_array(half_arg_t, const span<const uint16_t>& s,
                     semantic_tag tag,
                     const ser_context& context,
                     std::error_code& ec); (39)

    bool begin_multi_dim(const span<const size_t>& shape,
                         semantic_tag tag,
                         const ser_context& context, 
                         std::error_code& ec); (40)

    bool end_multi_dim(const ser_context& context,
                       std::error_code& ec); (41) 

(1) Flushes whatever is buffered to the destination.

(2) Indicates the begining of an object of indefinite length.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(3) Indicates the begining of an object of known length. 
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(4) Indicates the end of an object.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(5) Indicates the beginning of an indefinite length array. 
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(6) Indicates the beginning of an array of known length. 
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(7) Indicates the end of an array.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(8) Writes the name part of an object name-value pair.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(9) Writes a null value. 
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(10) Writes a boolean value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(11) Writes a text string value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(12) Writes a byte string value `source` with a generic tag.
Type `ByteStringLike` must be a container that has member functions `data()` and `size()`, 
and member type `value_type` with size exactly 8 bits (since 0.152.0.)
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(13) Writes a byte string value `source` with a format specific tag, `ext_tag`.
Type `ByteStringLike` must be a container that has member functions `data()` and `size()`, 
and member type `value_type` with size exactly 8 bits (since 0.152.0.)
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(14) Writes a non-negative integer value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(15) Writes a signed integer value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(16) Writes a half precision floating point value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(17) Writes a double precision floating point value.
Returns **true** if the consumer wishes to receive more events, **false** otherwise.
Throws a [ser_error](ser_error.md) on parse errors. 

(18)-(33) Same as (2)-(17), except sets `ec` and returns **false** on parse errors.

#### Private event consumer interface

    virtual void visit_flush() = 0; (1)

    virtual bool visit_begin_object(semantic_tag tag, 
                                    const ser_context& context, 
                                    std::error_code& ec) = 0; (2)

    virtual bool visit_begin_object(std::size_t length, 
                                    semantic_tag tag, 
                                    const ser_context& context, 
                                    std::error_code& ec); (3)

    virtual bool visit_end_object(const ser_context& context, 
                                  std::error_code& ec) = 0; (4)

    virtual bool visit_begin_array(semantic_tag tag, 
                                   const ser_context& context, 
                                   std::error_code& ec) = 0; (5)

    virtual bool visit_begin_array(std::size_t length, 
                                   semantic_tag tag, 
                                   const ser_context& context, 
                                   std::error_code& ec); (6)

    virtual bool visit_end_array(const ser_context& context, 
                                 std::error_code& ec) = 0; (7)

    virtual bool visit_key(const string_view_type& name, 
                           const ser_context& context, 
                           std::error_code&) = 0; (8)

    virtual bool visit_null(semantic_tag tag, 
                            const ser_context& context, 
                            std::error_code& ec) = 0; (9)

    virtual bool visit_bool(bool value, 
                            semantic_tag tag, 
                            const ser_context& context, 
                            std::error_code&) = 0; (10)

    virtual bool visit_string(const string_view_type& value, 
                              semantic_tag tag, 
                              const ser_context& context, 
                              std::error_code& ec) = 0; (11)

    virtual bool visit_byte_string(const byte_string_view& value, 
                                   semantic_tag tag, 
                                   const ser_context& context,
                                   std::error_code& ec) = 0; (12)

    virtual bool visit_byte_string(const byte_string_view& value, 
                                   uint64_t ext_tag, 
                                   const ser_context& context,
                                   std::error_code& ec); (13)

    virtual bool visit_uint64(uint64_t value, 
                              semantic_tag tag, 
                              const ser_context& context,
                              std::error_code& ec) = 0; (14)

    virtual bool visit_int64(int64_t value, 
                             semantic_tag tag,
                             const ser_context& context,
                             std::error_code& ec) = 0; (15)

    virtual bool visit_half(uint16_t value, 
                            semantic_tag tag,
                            const ser_context& context,
                            std::error_code& ec); (16)

    virtual bool visit_double(double value, 
                              semantic_tag tag,
                              const ser_context& context,
                              std::error_code& ec) = 0; (17)

    virtual bool visit_typed_array(const span<const uint8_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (18)

    virtual bool visit_typed_array(const span<const uint16_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (19)

    virtual bool visit_typed_array(const span<const uint32_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (20)

    virtual bool visit_typed_array(const span<const uint64_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (21)

    virtual bool visit_typed_array(const span<const int8_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (22)

    virtual bool visit_typed_array(const span<const int16_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (23)

    virtual bool visit_typed_array(const span<const int32_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (24)

    virtual bool visit_typed_array(const span<const int64_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (25)

    virtual bool visit_typed_array(half_arg_t, 
                                   const span<const uint16_t>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (26)

    virtual bool visit_typed_array(const span<const float>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (27)

    virtual bool visit_typed_array(const span<const double>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (28)

    virtual bool visit_typed_array(const span<const float128_type>& data, 
                                   semantic_tag tag,
                                   const ser_context& context, 
                                   std::error_code& ec); (29)

    virtual bool visit_begin_multi_dim(const span<const size_t>& shape,
                                       semantic_tag tag,
                                       const ser_context& context, 
                                       std::error_code& ec); (30)

    virtual bool visit_end_multi_dim(const ser_context& context,
                                     std::error_code& ec); (31)

(1) Allows producers of json events to flush any buffered data.

(2) Handles the beginning of an object of indefinite length.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(3) Handles the beginning of an object of known length.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(4) Handles the end of an object.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(5) Handles the beginning of an array of indefinite length.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(6) Handles the beginning of an array of known length.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(7) Handles the end of an array.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(8) Handles the name part of an object name-value pair.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(9) Handles a null value.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(10) Handles a boolean value. 
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(11) Handles a string value.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(12) Handles a byte string value associated with a generic tag.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(13) Handles a byte string value associated with a format specific tag.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(14) Handles a non-negative integer value.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(15) Handles a signed integer value.
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(16) Handles a half precision floating point value. 
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

(17) Handles a double precision floating point value. 
Returns **true** if the producer should generate more events, **false** otherwise.
Sets `ec` and returns **false** on parse errors. 

#### Parameters

`tag` - a jsoncons semantic tag
`context` - parse context information including line and column number
`ec` - a parse error code

#### Exceptions

The overloads that do not take a `std::error_code&` parameter throw a
[ser_error](ser_error.md) on parse errors, constructed with the error code as the error code argument
and line and column from the `context`. 

The overloads that take a `std::error_code&` parameter set it to the error code and return **false** on parse errors.

### See also

[semantic_tag](semantic_tag.md)  

[basic_default_json_visitor](basic_default_json_visitor.md)  

[basic_json_filter](basic_json_filter.md)  

[byte_string_view](../byte_string_view.md)  
